The data type Number(28,15) is sometimes unprecise when selected from PL/SQL developer.
-- Create table
create table NUMBERTEST
(
c1 number,
c2 NUMBER(28,15),
c3 NUMBER(28,10)
);
insert into NUMBERTEST select 495.96, 495.96, 495.96 from dual;
select c1, c2, c3...